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Difficulty: MediumAlkanoic Acids, Esterification, Saponification, Fats, and Oils

An organic compound XX with the molecular formula C4H8O2\text{C}_4\text{H}_8\text{O}_2 reacts with aqueous sodium hydroxide upon heating to yield ethanol and a salt YY. What is the IUPAC name of compound YY?

  1. Sodium ethanoateAnswer
  2. B
    Ethanoic acid
  3. C
    Sodium propanoate
  4. D
    Sodium methanoate

Answer

Sodium ethanoate
Alkaline hydrolysis of the four-carbon ester ethyl ethanoate (CH3COOCH2CH3\text{CH}_3\text{COOCH}_2\text{CH}_3) with sodium hydroxide breaks the ester linkage to produce ethanol (C2H5OH\text{C}_2\text{H}_5\text{OH}) and the sodium salt of ethanoic acid, which is sodium ethanoate (CH3COONa\text{CH}_3\text{COONa}).

Step-by-Step Solution

1
Identify the structure of the ester from its molecular formula and hydrolysis alcohol product.
The ester has molecular formula C4H8O2\text{C}_4\text{H}_8\text{O}_2 and produces ethanol (C2H5OH\text{C}_2\text{H}_5\text{OH}). The alkyl group attached to oxygen contains 2 carbons, leaving 2 carbons for the acyl group. Thus, the ester is ethyl ethanoate (CH3COOCH2CH3\text{CH}_3\text{COOCH}_2\text{CH}_3).
Esters have the general formula RCOOR′\text{RCOOR}', where R′OH\text{R}'\text{OH} is the alcohol component.
2
Determine the products of alkaline hydrolysis.
Heating ethyl ethanoate with aqueous sodium hydroxide (NaOH\text{NaOH}) cleaves the ester link to yield ethanol and sodium ethanoate (CH3COONa\text{CH}_3\text{COONa}).
Alkaline hydrolysis (saponification) yields the alcohol and the alkali metal salt of the alkanoic acid.

Key Concept

Alkaline Hydrolysis (Saponification) of Esters
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Topics

Alkanoic Acids, Esterification, Saponification, Fats, and Oils

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